Improved method of dyeing cellulosic fibers with indocarbon black sulfur dyestuff



nite States IMPROVED METHOD OF DYEING CELLULOSIC FIBERS WlTI-IINDOCARBON BLACK SULFUR DYESTUFF Glenn F. Womble, Danville, Va.,assignor, by mesne assignments, to Martin-Marietta Corporation, Chicago,Ill., a corporation of Maryland No Drawing. Filed July 22, 1959, Ser.No. 828,689

3 Claims. (Cl. 837) 'Bommer, Haller, and Pool described a method ofdyeing fibers of all kinds with certain vat dyestuffs including theproducts of sulfurization of carbazole-p-nitrosophenol by first making adyeing and thereafter treating the substantially fully developed dyedfibers with a diazo compound in the presence of an excess of sodiumacetate. The Homer et al. method has the disadvantage of failing toproduce good properties of fastness to chlorine, peroxide and the like.

The process of this invention is particularly advantageous in yarndyeing machines wherein fluid, i.e., the dye liquor, wash liquor, etc.,is circulated through yarn packages or beams. The yarns dyed in suchmachines are ordinarily woven with white or colored yarn into variousdesigns such as striped, checkered, and plaid fabrics which arechlorineand/or peroxide-bleached. Thus, the dyed yarns must possesssubstantial resistance to bleaching. Sulfur color dyeings arenotoriously unstable to the action of bleaching agents and heretoforehave been employed only in those areas of use wherein there is nonecessity or desire for bleaching. Almost all commercial machine dyeingof cotton yarn for obtaining optimum fastness properties has heretoforebeen done with expensive anthraquinone vat colors, especially whendyeing blacks.

One object of this invention is to obviate the disadvantages encounteredin the prior methods of treating sulfur color dyed fibers with diazocompounds.

Another object of the invention is to provide a process of dyeing yarnswith Indocarbon black sulfur colors to .obtain fastness properties equalor in some cases superior to those obtained with good anthraquinone vatcolors.

Another object is to provide yarns and a process of dyeing yarns whichwhen made into checks, plaids, and the like with white yarn and thenbleached, for example, with hydrogen peroxide, do not bleedobjectionably into the white areas.

Another object of the invention is the production of yarn-dyed wovenpatterns such as checkered, plaid, and similar fabrics at a greatlyreduced color cost.

Other objects are to provide yarns and a process of dyeing yarns withsulfur colors to obtain improved fastness properties without substantialsacrifice in tensile strength.

Other objects of the invention will be more readily apparent from thefollowing detailed description of the invention.

Broadly, the process of this invention, described in atent ice PatentedJuly 10, 1962 reference to Indocarbon black dyes, includes oxidizing theleuco form of an lndocarbon black sulfur color as applied to fibers, toan intermediate but still reactive stage, with air and treating theso-oxidized dyeing with a diazo compound under substantiallynon-oxidizing conditions. I have found that when the leuco Indocarbonblack sulfur color dyed fibers are treated with a diazo compound, thefibers are degraded as evidenced by a lower tensile strength. I havealso found that Indocarbon black sulfur color dyeings, which have beenoxidized in the usual manner, are in a substantially fully developedstate of oxidation, i.e., beyond the intermediate stage and at which nosubstantial further rapid oxidation takes place under ordinaryconditions of use. No improvement in bleach-fastness is obtained aftertreating such substantially fully developed, or oxidized, dyeings with adiazo compound.

Specifically, this invention is based on the remarkable discovery thatair-oxidation of the leuco Indocarbon black as well as certain othersulfur colors, when applied to materials being dyed, to an intermediatestage provides much improved fastness to bleaching after reaction with adiazo compound. The dyed fibers furthermore undergo no significant lossof tensile strength.

Intermediate oxidation by air is carried out in any suitable mannerwhich will leave a portion of the sulfur color in thenot-completely-oxidized form.

After oxidation by air, it is'important to prevent any substantialfurther oxidation of the Indocarbon black sulfur color. Although theexact theory or detailed reaction mechanism underlying the resultsobtained by my novel process 11218111011 been definitely established, itis believed that a range or degree of oxidation between the leuco andsubstantially fully developed state is necessary' to achieve optimumresults. Oxidation with air for periods ranging from about ten minutesup to twentyfour hours, for example, is unique in providing that levelof oxidation which results in outstanding bleach-fastness withoutdamaging the strength of the dyed fibers during treatment with the diazocompound. Any substantial oxidation beyond the level just described andtoward the substantially fully developed state of oxidation by extendedexposure to air or by treatment with chemical oxidants prior to orduring treatment with the diazo compound decreases the degree ofbleach-fastness in the resulting dyeings.

The usual practice in prior art dyeing with many sulfur colors inpackage and beam dyeing machines is to develop the color by the use ofchemical oxidants as opposed to air. However, the chemical oxidants,e.g., sodium perborate, hydrogen peroxide, ammonium persulfate and thelike, as ordinarily employed, oxidize the sulfur dyeings beyond thelevel required for successfully carrying out the present invention. VFurthermore, when such chemical oxidants are employed in attempts tooxidize the sulfur dyeings to an intermediate stage, the oxidation isdifiicult, if not impossible, to control practically. However, airforced into the dyeing machine and through the yarn oxidizes the appliedleuco sulfur dye to an intermediate stage and, thus, is unique.

After air oxidation to an intermediate stage just described, theIndocarbon black dyeing is then treated with a diazo compound preparedby methods conventionally employed in naphthol dyeing, but preferablywithout neutralization of the mineral acid used in the diazotization.However, any substantial additional oxidation should be avoided.

One possible source of oxidizing power during treatment with thediazocompoundis any residual nitrous acid (or nitrite convertible to nitrousacid) remaining from the diazotization in preparing the diazo compound.Residual spasms nitrous acid is advantageously removed by adding to thediazo solution an agent which will react with the nitrous acid andeliminate the nitrogen (or nitrite). Particularly 1 useful materials foreliminating residual nitrous acid innot 'fully understood, the reactionhas been found to be necessary in the attainment of bleach-fast dyeings.The usual sulfur dyeings, i.e., those which are normally prepared forend use, e.g., in a fabric, being in a fully developed state ofoxidation, have not been observed to evolve a gas when treated with thediazo compound.

The Indocarbon black sulfur colors employed herein have the PrototypeNo.- 126, and the New Color Index No. Sul. Blk. 11. They are availablecommercially as SoDyeCo Fast Liquid Black G, SoDyeCo Fast Liquid BlackR, and Indocarbon CLGS 1 Liquid.

Preparation of the dyebath and Indocarbon black sulfur color leucodyeings therefrom are carried out according to well-known methods or anyother suitable method.

The diazo compounds, otherwise known as diazotized amines, are preparedin accordance with conventional procedures. In general, diazo compoundsare usually pre- Manufacturers Name Chemical Name Fast Scarlet G Basep-nitro-o-toluidine.

5-nitro-2-anisidine. Fast Scarlet TR Base 3-ehloro-2-methylani1ine. FastScarlet LG Base benzyl -l-methyoxy -2 amino- Fast Scarlet RC Basephenyl-t-sulfone. p-nitro-o-anisidine. Fast Red RC Base Fast Red GG Basep-ehloro-oanisidine.

p-nitro-aniline.

ru-nitro-p-toluidiue.

p-ehloro-o-nitroaniline.

m-nitro-o-toluidine.

p-nitro-o-anisidine.

5-ehloro-2-arninotoluene.

diethyl sulfonamido-o-anisidine.

p-chloro-o-toluidi.ne.

4-ehl0r0-2 arninodiphenyl oxide.

m-nitro-p-anisidine.

o-aminoazotoluene.

dianisidine.

5-amino-2-benzoylamino-l,4-

diethoxy benzene.

2,4-dichl0roaniline.

o-anisidine azo-a-naphthylamine.

o-nitroaniline.

Fast Red FG Base Fast Bordeaux GP Base.

Fast Blue BB Base- Fast Black LB Base Fast Orange GR Base While theprocess of this invention is generally applicable to the dyeing of anyfibers, capable of being dyed with sulfur colors ordinarily used oncotton and the like, in woven or unwoven form, it is particularlyadaptable to dyeing cellulosic fibers and especially, cotton fibers.Fibers dyed in accordance with theprocess of this invention can betreated with such agents as chlorine or hydrogen peroxide without anysubstantial loss of color.

My process is particularly useful in dyeing cotton yarns which are to beinterwoven with white yarns or other colored yarns to form a fabrichaving a certain design. Cellulose textile fabrics, yarns, or knittedgoods thus made and comprising interwoven white (or other coloredyarns),

1 Trademark.

4 especially cotton yarns, dyed by my process are characterized by theability to be bleached without the dyed yarns running and/or stainingappreciably the adjacent white yarns.

Improved bleach and Wash fastness without substantial impairment oftensile strength is also obtained with other sulfur colors when employedin accordance with the process for dyeing with Indocarbon blacks asdescribed herein. The following list illustrates the various sulfurcolors which are advantageously employed in place of the Indocarbonblack sulfur colors in the process as described herein.

Color Part I- Manutacturer's Name Index or New Color Prototype Index No.

Sulfogene 1 Brown 0143 Pr. 702- Sul. Red 5. SoDyeSul Liquid Yellow ECF955 Sul. Yell. 4. SoDyeSul Liquid Brown FLCF Pr. 702.-.- Sul. Red 5.SoDyeSul Liquid Green BGOF Sul. Green 16. SoDyeSul 1 Liquid Green NJ 1Trademark.

The following examples are presented. In the examples, percentagesunless otherwise specified are based on the weightof fiber beingtreated. Chlorine gradients:

Anhydrous disodium phosphate g./l 10 Borax g./l 5 Calcium chloride g./l0.2 28% aqueous hydrogen peroxide cc./l 12.5

This solution has a pH of about 10 and titrates 4.5 to 5 g./l. hydrogenperoxide. The fiber wrapped in the white cloth is then inserted into atube, and the tube is stoppered with provision for exhaust vapors. Thetube is then placed in a boiling water bath as a means of heating, forone hour. The hydrogen-peroxide bleaching described above is essentiallythe same as bleaching conducted in textile plants.

Bleach-treated fibers, whether treated by chlorine or hydrogen peroxide,were then visually compared with unbleached, dyed fibers to determinethe degree of color loss. No substantial degree of color loss designatesexcellent bleach fastness, noticeable but minor color loss designatesgood bleach fastness, substantial color loss designates fair bleachfastness and almost total color loss designates poor bleach fastness.Also, as an indication of bleach fastness, the white cotton swatcheswrapping the dyed fibers and subjected to the hydrogen-peroxidebleaching were inspected. Substantially no coloring of the white clothdesignates excellent bleach fastness, barely noticeable discoloration ofthe white cloth designates good bleach fastness, substantial coloring ofthe white cloth designates fair bleach fastness and substantially heavycoloring of the white cloth designates poor bleach fastmess.

The bases with the exception of Fast Scarlet GG were diazotized in theusual manner. The Fast Scarlet GG Base, 7

being an exception to the ordinarily used diazotizing procedure, wasdiazotized by dissolving 1 gm. of the base in about 2 ml. of glacialacetic acid to form a solution which is added with stirring to 31 gm. ofa water-ice mixture containing 4.4 ml. of 32% aqueous hydrochloric acidand 0.5 gm. of Triton X-733 (an alkylarylpolyether alcohol). An aqueoussolution of 0.59 gm. of sodium nitrite is added to the solution thusobtained. The resulting solution is then stirred for to 30 minutes at atemperature of 35 to 40 F., after which time it is neutralized with 2.5gm. of sodium acetate.

Tensile strengths of the fibers were determined in the usual manner andany tensile strength relationships given in the examples were based onan average of 10 single-end breaks.

The symbols g./l. and cc/l. wherever employed herein designate grams perliter and cubic centimeters per liter, respectively. Temperatures unlessotherwise indicated are on the Fahrenheit Scale. Wherever employedherein, the term fibers designates fibers regardless of the form theyare in, for example, woven or unwoven, and includes fabrics as well asyarns. 7

40/2 cotton yarn was placed in a Gaston County Yarn Dyeing Machine(giving a liquor ratio of yarn to dye- .bath of 1 to 7.5), wetted outwith an aqueous wetting solution containing 2 cc./l. wetting agent forminutes at 180 F., rinsed with water and heated to 160 F.

An aqueous solution of sodium sulfide flakes (3% based on the weight ofyarn) was added to the machine and circulated through the yarn for 10minutes. A dyebath, SoDyeCo Fast Liquid Black R for Example 1 and 30%SoDyeCo Fast Liquid Black G for Examples 2 through 6, was then added tothe machine in two portions. The dyebath was circulated alternately for7 minutes outside-in and for 3 minutes inside-out, thus providing a 10minute cycle. The dyebath was circulated in this manner for 20 minutes,after which time 30 g./l. common salt was slowly added on .the outsideinportion of the cycle. The dyebath was circulated in this manner for anadditional 20 minutes, after which time it was removed and a coldrunning Water wash was applied with Water entering through the expansiontank, passing through the yarn, and then passing out through the drain.The cold water running wash was continued for 20 minutes.

The dyed yarn in all examples thus treated, was then oxidized by forcingcompressed air through theyarn for 10 minutes at room temperature.

The dyed yarns were then treated with the diazotized base orcorresponding salt correspondingly listed in Table I, employing theamount of base (in percentages, based on the weight of yarn) ascorrespondingly listed in said table. The Scarlet GG base was preparedas described above. However, in Examples 1, 2, 4, and 6, no sodiumacetate was used in the diazotized base solution. Instead,

1.2% of sulfamic acid was employed to free the diazotized.

the amount of sodium acetate specified above in the dia-:

zotization process.was employed. The yarn was rinsed with water andsoap'ed in the usual manner with solution containing 2 g./l. of soda ashand l g./l. sodium oleyl taurine (Igepon T-33) at 190 F. for 30minutes.The yarn was then finally rinsed.

There was obtained'in each example a. heavy black shade.

The yarn of each example, after the treatment described above, was thentested for bleach fastness and tensile strength. The results of thebleach-Easiness tests are listed correspondingly in Table I. The tensilestrengths of the yarns were not impaired and compared favorably withyarns dyed in a conventional manner.

In each of Examples 1 through 3, a sample of the dyed yarn, as acontrol, was removed before oxidation, treated with the diazotized baseas described above, rinsed with Water, soaped and rinsed again. Thetensile strengths of these samples were considerably lower than thetensile strengths of the corresponding air-oxidized, diazotizedbase-treated yarns. The chlorineand peroxidebleach fastness of thecontrol sample was substantially equivalent to that of the air-oxidized,diazotized basetreated yarns.

In each of Examples 5 and 6, a sample of the yarn after oxidation wasremoved from the machine before the rest of the load was treated withthe diazotized base and the sample soaped and rinsed in the mannerdescribed above. These samples served as controls and were sub- .jectedto the bleaching test and tensile strength test.

Each of the control samples lost a considerable depth I of shade afterchlorineand hydrogen-peroxide bleaching and bled profusely onto thewhite cloth wrapping in the hydrogen-peroxide bleach test. The controlsamples after chlorine bleaching had almost completely lost theiroriginal black color. The control samples after hydrogenperoxidebleaching had lost less color when compared with those subjected tochlorine bleaching, but had bled profusely onto the white cloth wrappingemployed in the peroxide bleach tests. The tensile strengths of thecontrol samples were no better than the tensile strengths of theair-oxidized and diazotized base-treated yarn.

Examples 7 Through 9- In order to compare the results obtained byoxidizing the sulfur dyeing with air, with results obtained by oxidizingsulfur dyeings with chemical oxidants, the procedure of Examples 1through 6 was repeated with the exception that instead of oxidizing withcompressed air for 10 minutes at room temperature, the sulfur dyeing wasoxidized with 5% sodium perborate for '15 minutes at F. prior totreatment with the diazotized base. Example 7 employed 30% SoDyeCo FastLiquid Black and Examples 8 and 9 employed 30% SoDyeCo Fast Liquid BlackG. Table II below shows the diazotized base or corresponding salt andthe amount of diazotized base or salt correspondingly employed in eachof Examp1es7 through 9. In each example, a sample of yarn was removedafter oxidation with the sodium perborate but prior to treatment withthe diazotized base. There was obtained in each example a heavy blackshade. The yarns obtained in each example and the samples not treatedwith thediazotized base were tested for chlorineand hydrogen-peroxidebleach 'fastness and also for tensile strength. Table II provides theresults of the bleach-fastness tests.

TABLE II Diazotized Ex. Diazotlzed Base Kind Base Bleach Amount Fastness(Percent) Yellow G0 3.75 Scarlet GG 3.0 533;. 12.0 poor.

1 Black G and 3% Sodium sulfide flakes.

dyed by immersing in the dyebath and intermittently turning them for 20minutes while maintaining the dyebath at 1 60" F. then adding 30 g./l.of common salt,

* Examples I and '11 These examples show that by OXidiZing withpotassium bichrornate instead of compressed air as an after treatmentfor the sulfur dye, but prior to treatment with the diazotized base,fails to result in good bleach fastness.

In each of Examples 10 and 11, two 10 gm. skeins of 40/2 raw. cottonyarn were wetted out at room temperature in an aqueous solution of asynthetic wetting agent in the usual manner. The skeins were thenrinsed, squeezed through a wringer to remove excess water and enteredinto dye-pots having a liquor ratio of 1 part by Weight of cotton to 7/2 parts by weight of dyebath. The dyebath in each example'contained 30%SoDyeCo Fast Liquid Black G. The yarn was dyed with intermittent turningfor minutes at 160 F. After this time, g./l. common salt was added andthe yarn turned for an additional 20 minutes. Then the yarn was removed,rinsed in tap water and oxidized by immersing it' in an aqueoussolution, containing 2% potassium bichrornate based on the weight ofyarn in Example 10,

and 4% potassium bichromate in Example 11, for a period and l g./l. ofIgepon T-33 at 200 F. for 30 minutes and finally rinsed with, first hotand then cold water. There was obtained a deep black shade.

The tensile strengths of the yarns thus obtained were found to beunimpaired when compared with yarns treated with the sulfur dye andoxidized with potassium bichromate in the same manner but not treatedwith the diazoti zed base. The yarns thus treated, a well as similaryarns not treated with the diazotized base, showed poor fa'stness-tochlorineand hydrogen-peroxide bleaching.

7 Example 12 Four 10 gm. skeins of two-ply spun vicose yarn were dyed inthe following manner. The skeins were wetted out ,at room temperature ina conventional wetting agent, rinsed, sqeezed through a wringer toremove excess water, and entered into dye-pots having a liquor ratio of1 part by weight of yarn to 7.5 parts by weight of dyebath. The dyebathcontained 25% SoDyeCo Fast Liquid The skeins were and intermittentlyturning for an additional 20 minutes. The skeins were removed and rinsedin cold water. Skeins 1 and 2 were oxidized by air atroom temperaturefor one hour. Skein 3 was oxidized with a sodium perborate solutioncontaining 5% (based on the weight of yarn) sodium perborate. Skeins 2and 3 were rinsed with water and entered into a solution containingdiing, turning greenish-gray and gray, respectively, on, bleaching withchlorine, and badly staining the white cloth wrapper in theperoxide-bleach test. Skein 2 was greatly improved in f astness tochlorine and hydrogenperoxide bleaching. The tensile strengths of theyarns of skeins l, 2 and 3 were all of substantially the same highmagnitude. The tensile strength of the yarn of skein 4 was considerablylower than that of any of the other Skeins.

Examples 13 Through 18 The procedure of dyeing employed in Example 12for dyeing skein 2 was repeated on cotton yarn. The dyeings thusobtained were air oxidized (with the exception of Example 13, which wasnot oxidized) at room temperature for the times indicated in the tablebelow. The dyeings thus obtained and oxidized were then treated with thediazotized base as described in' Example 12, rinsed with water andsoaped in the usual manner. The yarns of all the examples carried a deepblack shade. Chlorine-l bleach tests, peroxide-bleach tests and tensilestrength determinations weremade on the yarns thus obtained. The resultsof the bleach tests are listed correspondingly in the table below.

The tensile strengths. of the yarns of Examples 14 through 18 were ofsubstantially thesame high magnitude. The'tensile strength of the yarnof Example 13 was, however, considerably lower than those of the yarnsin Examples 14 through 18 Example 19 Employing a procedure similar tothat described in Examples 1 through 6, a 2 1b.. load of 40/2 cottonyarn was dyed with 25% SoDyeSul- Liquid Brown FLCF (Pr. 702 and Sul Red5), air-oxidized and treated with 3% Scarlet GG Base employing l.'2%sulfarnic acid instead of sodium acetate. treated, when subjected tobleach-fastness tests provided good results.

azotized 2,5dichloroaniline in the amount. of 3% and" sulfamic'acid inthe amount'of 1.2%. Skein 4 was not oxidized ,afiter dyeing but wasentered directly after rinsing into the diazotized base. with thediazotized base.

Skein l'was not treated Skeins 1 and Yarn-dyed in the same manner butoxidized with 5% sodium perborate for 15 minutes at F. instead of airprior to treatment with the diazotized base gave poor results in thebleach-fastness tests. The tensile strengths of the treated,air-oxidized, dyed yarns and the treated, sodium perborate-oxidized dyedyarns were about the same. A sample of the dyed yarn was removed beforeoxidation,-.treated with the diazotized amine and after-treated asdescribed above, The tensile strengths of these'unoxid'ized yarns wereconsiderably lower than the tensile strength of the diazotized aminetreated; air-oxidized, dyed yarns. a The bleach-fastness oftheunoxidized yarns was substantially equivalent to that of thediazotized amine-treated, airvoxidized, dyed yarns.

, Example 20 v An approximate 2 lb. load of 40/2 cotton yarn was placed'in' a Gaston County Yarn Dyeing Machine, wetted out with a solutioncontaining 2 cc./l. wetting agent for twenty minutes at 180 F., rinsedwith water and heated to F. An aqueous solution ,of sodium sulfideflakes (3% basedon the weight of yarn) was added to the mar, chine andcirculated through the yarn for ten minutes;

The yarn,.thus dyed, oxidized and A dye solution was prepared by boiling'2 /2% Sulfogene Brilliant Green I (Concentrated) with 5% sodium sulfideflakes and 2 /2% soda ash employing about 400 cc. of water. The dye bathwas added to the dyeing machine and circulated alternately for sevenminutes outside-in and for three minutes inside-out, thus providing aten minute cycle. The dye bath was circulated in this manner for twentyminutes, after which time 30 g./l. common salt was slowly added on the"outside-in portion of the cycle. The dye bath was circulated in thismanner for an additional twenty minutes, after which time it was removedand a cold running water wash was applied with water entering throughthe expansion tank, passing through the yarn and then passing outthrough the drain. The cold water running wash was continued for twentyminutes. The yarn thus treated was then oxidized by forcing compressedair through the yarn for ten minutes at room temperature.

The yarn was then treated with 3% diazotized Fast Scarlet 66 Base. Thediazotized base was prepared as described above except that 1.2%sulfamic acid was added in place of the sodium acetate used in the abovedescription. The yarn was rinsed with water and soaped in the usualmanner with a solution containing 2 g./l. of soda ash and 1 g./l. sodiumoleyl taurine (Igepon T-33) at 190 F. for thirty minutes. The yarn wasthen finally rinsed. The treated yarn after dyeing, oxidizing andtreated with the diazotized amine developed a bright deep green shadewhereas the untreated yarns, after dyeing and oxidizing, were dull inappearance and somewhat light in shade. As a control, cotton yarn dyedand oxidized but not treated with the diazo base as described above wassubjected to bleach tastness and tensile strength tests along with thedyed, oxidized, treated yarns. The chlorine bleach resistance of theuntreated yarn was poor whereas the chlorine bleach fastness of thetreated yarn was good to excellent. The peroxide bleach fastness of thetreated yarn was excellent, having lost little or no color and bleedingto only a slight degree onto its white cloth wrapper. The untreatedyarn, however, lost a considerable amount of color and stained its whitecloth wrapping severely in the peroxide bleach test. The tensilestrengths of both the untreated and treated yarns were of the samegeneral magnitude with the treated yarns being somewhat higher intensile strength. Unexpectedly, the dyed, oxidized and treated yarndeveloped an even brighter, deeper green shade after peroxide bleachingthan it originally had.

Example 21 Employing the same procedure of dyeing set forth-in Example12, three skeins of cotton yarn were dyed with 20% SoDyeSul Liquid GreenNI. After dyeing and rinsing in cold water, the skeins were treated asfollows.

Skein 1 was air oxidized at room temperature for more than an hour,skein 2 was oxidized with air at room temperature for about one hour andthen treated with 3% diazotized Scarlet GG Base containing 1.2% suifamicacid and skein 3 was not air oxidized to any great extent (other thanswitching the skein from the dyebath to the rinse water and thence tothe diazotized amine solution) but was treated with a diazotized aminein the same manner as skein 2. All skeins were rinsed with water andsoaped in the usual manner.

Skein 1 developed a dark bluish-green color, skein 2 developed a darkyellowish-green color and skein 3 developed a somewhat lighteryellowish-green color. All skeins were subjected to the bleach fastnesstest. Skein 1 on chlorine bleaching turned to a light, sky blue color.Skeins 2 and 3 on chlorine bleaching became light green in color withskein 3 being slightly lighter than skein 2. On peroxide bleaching skein1 turned to a blue shade of moderate depth and severely stained itswhite cloth wrapping, and skeins 2 and 3 lost some of their originalyellowish-green color and only slightly stained their white clothwrappings. The tensile strengths of all skeins were approximately thesame.

The process of the present invention has been described hereinabove withreference to air as the oxidizing medium but it is to be understood thatthis is for illustrative purposes only and that other oxidizing agentsor media are contemplated within the scope of this invention as definedin the appended claims.

What I claim is:

1. An improved method of dyeing cellulosic fibers with Indocarbon blacksulfur dyestulf, said fibers having improved fastness to both peroxideand chlorine bleaching without impairment of the tensile strength,comprising the steps of impregnating the fibers with the leuco form ofsaid dyestufl, oxidizing said dyestutf to the intermediate stage ofoxidation, treating said fibers with a diazotized amine undersubstantially non-oxidizing conditions, rinsing the fibers with water,soaping the fibers under alkaline conditions, and thereafter againrinsing the fibers with Water.

2. A method as defined in claim 1, and in which the method is carriedout in a yarn package dyeing machine and the dyestufl is oxidized to theintermediate stage of oxidation by forcing compressed air through thefibers for 10 minutes at room temperature.

3. Cellulosic textile fibers dyed according to the method defined inclaim 1.

References Cited in the file of this patent UNITED STATES PATENTS1,874,099 Haller Aug. 30, 1932 1,879,727 Haller et al Sept. 27, 19322,280,900 Dreyfus Apr. 28, 1942 2,344,625 Lubs et a1. Mar. 21, 19442,382,188 Vincent et a1 Aug. 14, 1945 2,912,298 Carroll et al Nov. 10,1959

1. AN IMPROVED METHOD OF DYEING CELLULOSIC FIBERS WITH INDOCARBON BLACKSULFUR DYESTUFF, SAID FIBERS HAVING IMPROVED FASTNESS TO BOTH PEROXIDEAND CHLORINE BLEACHING WITHOUT IMPAIRMENT OF THE TENSILE STRENGTH,COMPRISING THE STEPS OF IMPREGNATING THE FIBERS WITH THE LEUCO FOR OFSAID DYESTUFF, OXIDIZING SAID DYESTUFF TO THE INTERMEDIATE STAGE OFOXIDATION, TREATING SAID FIBERS WITH A DIAZOTIZED AMINE UNDERSUBSTANTIALLY NON-OXIDIZING CONDITIONS, RINSING THE FIBERS WITH WATER,SOAPING THE FIBERS UNDER ALKALINE CONDITIONS, AND AND THEREAFTER AGAINRINSING THE FIBERS WITH WATER.